Artur Beterbiev and Dmitry Bivol will put their undefeated professional records on the line as they seek to become the undisputed light-heavyweight champion of the world in Riyadh on Saturday.
Both are veterans of the ring and former Russian amateur teammates.
Both have flawless professional careers, with Kyrgyzstan-born and California-based WBA champion Bivol, 33, boasting a 23-0 record with 12 knockouts.
Russian-born Canadian Beterbiev, 39, has the WBC, IBF and WBO belts in an iron grasp with a 20-0 record, all by knockout or stoppage. No opponent has gone the distance against the bearded puncher.
The clash at the Saudi capital's Kingdom Arena, postponed from June after Montreal-based Beterbiev suffered a knee injury, will be the first time one man has owned all four major belts in the division.
The last undisputed light-heavyweight champion was American Roy Jones Jr. who beat Reggie Johnson to unify the WBA, WBC and IBF belts in 1999.
"I can't see anything but a thriller," Bivol's promoter Eddie Hearn told the BBC. "In 50-50 fights, which this really is, anything can happen.
"When you fight Beterbiev it's like a ticking time bomb... the speed of that time bomb depends on the opponent. Dmitry has the ability to make that tick really slow. How slow can he make it tick? The 'boom!' point is 12 rounds.
"The only person that can beat Artur Beterbiev right now is Dmitry Bivol. Nobody else. And he could do it."
Beterbiev's promoter Frank Warren has described the fight as a 'game of thrones'.
IBF cruiserweight champion Jai Opetaia of Australia is on the undercard with his first title defence against British underdog Jack Massey.
Saudi Arabia will also host a women's world title fight for the first time when Britain's Raven Chapman faces Australian WBC featherweight champion Skye Nicolson.
"I feel like we have a responsibility on our hands to put on a great show, and make sure that we're the first of many," Nicolson, 11-0, told DAZN.
